Touch Control Panel Assembly - Sharp R-1880LS Service Manual

The touch control section consists of the following units
as shown in the touch control panel circuit.
(1) Key Unit
() Control Unit
The principal functions of these units and the signals communicated
among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated in the LSI
are sent to the key unit through P00 - P06.
When a key pad is touched, a signal is completed through the key
unit and passed back to the LSI through AN1 and R4 - R7 to
perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchronizing
signal circuit, ACL circuit, buzzer circuit, temperature measure-
ment circuit, absolute humidity sensor circuit, relay circuit and
indicator circuit.
1) LSI
This LSI controls the temperature measurement signal, A H sensor
signal, key strobe signal, relay driving signal for oven function
and indicator signal.
2) Power Source Circuit
This circuit generates voltages necessary for the control unit
from the AC line voltage.
Symbol Voltage
VC -5.1V
VP -31V
and anode voltage
VF1 .9Vac
VF

TOUCH CONTROL PANEL ASSEMBLY

OUTLINE OF TOUCH CONTROL PANEL
Application
LSI(IC1)
Fluorescent display tube Grid
Filament of fluorescent
dis play tube
(VF1 to VF voltage)
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in order
to compose a basic standard time in the clock circuit. It in-
corporates a very small error because it works on commercial
frequency.
4) ACL Circuit
A circuit to generate a signals which resetting the LSI to the
initial state when power is applied.
5) Buzzer Circuit
The buzzer is responds to signals from the LSI to emit
audible sounds (key touch sound and completion sound).
6) Temperature Measurement Circuit : Oven
The temperature in the oven cavity is sensed by the thermistor.
The variation of resistance according to sensed temperature is
detected by the temperature measurement circuit and the result
applied to LSI. The LSI uses this information to control the
relay and display units.
7) Absolute Humidity Sensor Circuit
This circuit detects the humidity of a food which is being
cooked, to control its automatic cooking.
8) Door Sensing Switch
A switch to inform the LSI if the door is open or closed.
9) Relay Circuit
To drive the magnetron, heating element, fan motor, convection
motor, damper motor, turntable motor, hood motor, and light
the oven lamp and hood lamp.
10) Indicator Circuit
Indicator element is a Fluorescent Display.
Basically, a Fluorescent Display is triode having a cathode,
a grid and an anode. Usually, the cathode of a Fluorescent
Display is directly heated and the filament serves as cathode.
The Fluorescent Display has 8-digits, 16-segments are used
for displaying figures.
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R-1880LS/LST